Monday, August 31, 2015

Monterey Canyon is one of the deepest submarine canyons on the west
coast of the United States.
The canyon head lies just offshore of Moss
Landing on the Central California coast.
From there, the main channel
meanders over 400 kilometers seaward to a depth of more than 4,000
meters on the abyssal plain.
Repeated mapping in certain areas of the
canyon have shown that the terrain changes substantially every few
months due to large sediment-transport events involving both debris
flows and turbidity currents.
If the water drained from Monterey Bay,
the newly revealed terrain would be stunning, with cliffs, gorges,
valleys, and spires matching the scenery found in some of our most
beautiful national parks.

Sonar has long been used to map the seafloor, usually with equipment
mounted on a ship's hull.
The ship travels back and forth, sending sound
waves toward the ocean floor.
When the sound waves hit the bottom, they
bounce back to the surface, where the sonar receivers use the returned
signals to indicate the depths of the seafloor.
Modern multibeam sonars
use numerous narrow beams covering wide swaths of the seafloor to create
maps like the bathymetric map shown here.
The more detailed maps
overlaid on the base map were created with the Monterey Bay Aquarium
Research Institute's mapping autonomous underwater vehicle (AUV).
Although the AUV uses the same technology, it flies closer to the
bottom, allowing higher resolution maps to be made.
The AUV bathymetric
maps show details as small as one meter (three feet) across, and are
among the most detailed maps ever made of the deep seafloor.
Researchers
use the detailed maps to understand seafloor morphology and the
movement of sediment within submarine canyons.

Cross-sections of the Monterey Canyon (left) and Grand Canyon (right)
shown at the same scale demonstrate that these features are similar in
size and shape.

Both canyons are conduits through which massive volumes
of sediment move.

While water flowing in the Colorado River carved the
Grand Canyon, a directly analogous process is not known to have occurred
within Monterey Canyon.

Canyon life

Monterey Canyon and the waters above it provide a wide array of
habitats, from rocky outcrops and the soft seafloor to the dark
midwater, where there is little or no sign of light from above nor of
the seafloor below.
MBARI researchers often encounter rarely seen
biological communities, observe novel behaviors of deep-sea organisms,
and discover new species in the deep sea.